Electric resistance furnace



NOV. 24, 1931. J, MlLLAR ELECTRIC RESISTANCE FURNACE Filed Oct. 6, 1930 Invanr Patented Nev. 24. i931 v UNITED STATES PATENT OFFICE WILLIAI .TAKES MILLAB, F LONDON, ENGLAND ELECTRIC RESISTANCE FUEN'ACE Application lled October 3, 1930, Serial No. 486,831, and in Great Britain October 8, 1929.

When heating electric resistance A furnaces to temperatures higher than those for which nickel chrome resistors are suitable, it is customary to use non-metallic resistors which can' withstand high temperatures.

One of the chief diiculties with this type of resistor is to make a suitable connection between the cables carryingl the electrical supply and the resistors. As the resistors are at a very high temperature, it isnot convenient to make the connection inside the brickwork of the furnace, so that the resistor must be brought outside the brickwork.l

In order to cool the heads of the resistance '15 it has been vpreviously proposed .to provide spaces between the outside of the furnace walls and an outer casing through which air currents can flow.

According to the invention a recess is formed inthe brickwork of the furnace at each end of the resistors and holes are provided in a metallic casing, enclosing the brickwork, for the admission of atmospheric air into the direct contact withthe ends of the resistors, the current of air produced by conends of the resistors and a substantially vertical passage between the brickwork and casing for conveying away the current of air produced by convection.

2. An electric furnace according to claim 1, in which bale plates are provided in the, recesses to direct the air into contact with thev ends of the resistors.

In testimony whereof I have signed my name to. this specification.

WILLIAM JAMES MILLAR.

vection being discharged through'a vertical or substantially vertical passage between the brickwork and casing. v

The accompanying drawing shows dlagrammatically an example of avcooling device according to the invention.

A is the furnace, B a resistor, C the refracto brickwork, D connections between cables an the resistors.

u The brickwork is cut away as'shown at E and the endsof the resistors extend into the air space obtained by this means.

-Air enters through an opening F in the metal vcasing G and by the baille late H is o brought into contact with and coo the ends of the resistors, as it rises by convection in the path shown by the arrow and escapes by the verticalfspace I provided betweenthe casing G and a metal casing J provided at this part of the brickwork.

The arrangement according to the invention has the further advantage that it enables the greater part of the brickwork to be of'sutlicient thickness to form a satisfactory ,heat insulator without necessitating an abnor- 

